On the ultrastructure of the developing and adult mouse corneal stroma

Abstract

The EM study of the mouse embryonic cornea from the 12th to the 19th day of gestation as well as on postnatal days 2 and 18 and on adult animals allow the following conclusions to be drawn: 1. Immediately after the separation of the lens vesicle, the mesenchyme cells migrate into the cornea anlage. 2. There is no collagenous primary stroma in the mouse embryo. 3. During days 12-14 the stroma cells (fibroblasts) differentiate and develop the organelles required for ICS (intercellular substance) secretion. 4. In the posterior region of the stroma, the collagen fibrils are deposited in bundles approximately perpendicular to each other. 5. The adult mouse stroma is divided into 2 zones. In zone I the subepithelial fibrils are randomly distributed and are not bundled (rudimentary Bowman's membrane). In zone II the fiber bundles lie in the plane of the cornea and form a highly ordered three-dimensional network. Basic differences between the mouse and other species are discussed.

Anterior eye development and ocular mesenchyme: new insights from mouse models and human diseases

“…The cells form long cytoplasmic processes and have a stellate, star-shaped phenotype. (2) As the number of cells between the lens and surface ectoderm continuously increases, the cells condense more and more to form several layers of flat mesenchymal cells that are separated from each other by a loose fibrillar extracellular matrix (Fig. 1B).…”

Corneal development associated with eyelid opening

“…The endothelium remains a monolayer throughout the entire development of the cornea and gradually thins with age. However, changes do occur during the time surrounding eyelid opening that likely have a profound effect on the endothelium becoming non-proliferative and initiating its barrier function (Bahn et al, 1986;Cintron et al, 1988;Haustein, 1983;Joyce et al, 2002;Murphy et al, 1984). Through electron microscopic studies, it has been demonstrated that, just before eyelid opening, intracellular spaces close and junctional complexes mature.…”

Requirement for Pax6 in corneal morphogenesis: a role in adhesion

“…The adult cornea is a lamellar tissue consisting of a stratified surface epithelial layer, a collagenous stroma sparsely populated by keratocytes and an inner endothelial layer. Embryonically, a region of surface ectoderm defined by the lens placode gives rise to the corneal epithelium as well as to the lens, whereas the corneal stroma and endothelium develop from cells originating in the neural crest (Haustein, 1983;Pei and Rhodin, 1970;Pei and Rhodin, 1971;Trainor and Tam, 1995). In the mouse, the corneal epithelium continues to mature after birth: at two weeks of age, the epithelium expands from two cell layers to a self-renewing, stratified epithelium comprising eight to ten cell layers (Hay, 1979;Zieske and Wasson, 1993).…”